High-precision determination of the isotopic composition of dissolved iron in iron depleted seawater by double spike multicollector-ICPMS.
High-precision determination of the isotopic composition of dissolved iron in iron depleted seawater by double spike multicollector-ICPMS.
复制标题
双峰多接收器-ICPMS 高精度测定贫铁海水中溶解铁的同位素组成。
作者：
F. Lacan;A. Radic;M. Labatut;C. Jeandel;F. Poitrasson;G. Sarthou;C. Pradoux;J. Chmeleff;R. Freydier
这项工作证明了测量海水中溶解铁的同位素组成的可行性，铁浓度范围为0.05-1 nmol L（-1），允许在大多数海洋沃茨，包括铁贫沃茨的高营养低叶绿素地区的测量。它提出了一个详细的描述，我们以前公布的协议，显着改进的检测限和空白的贡献。使用次氮基乙酸超流树脂预浓缩铁，并使用AG 1-x4阴离子交换树脂纯化。同位素比用多接收器电感耦合等离子体质谱仪（MC-ICPMS）Neptune测量，其与去溶剂化器（Aridus II或Apex-Q）耦合，使用（57）Fe-（58）Fe双尖峰质量偏差校正。Monte Carlo检验表明，对于由约50%（57）Fe和50%（58）Fe组成的双加标物，以及样品与双加标物数量比约为1，可获得最佳精密度。对于20 - 2 L的样本量，总手术产率为91 ± 25%（2SD，n = 55）。程序空白范围为1.4 - 1.1 ng，样本量范围为20 - 2 L，分别转换为Fe浓度，分别对应于0.001和0.010 nmol L（-1）的空白贡献。海水样品和标准溶液重复测量的测量精度为0.08 ‰（δ（56）Fe，2SD）。精确度足以清楚地检测和量化海洋中的同位素变化，到目前为止，已观察到的变化范围为千分之2.5，从而为阐明海洋铁循环开辟了新的视角。
This work demonstrates the feasibility of the measurement of the isotopic composition of dissolved iron in seawater for an iron concentration range, 0.05-1 nmol L(-1), allowing measurements in most oceanic waters, including Fe depleted waters of high nutrient low chlorophyll areas. It presents a detailed description of our previously published protocol, with significant improvements on detection limit and blank contribution. Iron is preconcentrated using a nitriloacetic acid superflow resin and purified using an AG 1-x4 anion exchange resin. The isotopic ratios are measured with a multicollector-inductively coupled plasma mass spectrometer (MC-ICPMS) Neptune, coupled with a desolvator (Aridus II or Apex-Q), using a (57)Fe-(58)Fe double spike mass bias correction. A Monte Carlo test shows that optimum precision is obtained for a double spike composed of approximately 50% (57)Fe and 50% (58)Fe and a sample to double spike quantity ratio of approximately 1. Total procedural yield is 91 +/- 25% (2SD, n = 55) for sample sizes from 20 to 2 L. The procedural blank ranges from 1.4 to 1.1 ng, for sample sizes ranging from 20 to 2 L, respectively, which, converted into Fe concentrations, corresponds to blank contributions of 0.001 and 0.010 nmol L(-1), respectively. Measurement precision determined from replicate measurements of seawater samples and standard solutions is 0.08 per thousand (delta(56)Fe, 2SD). The precision is sufficient to clearly detect and quantify isotopic variations in the oceans, which so far have been observed to span 2.5 per thousand and thus opens new perspectives to elucidate the oceanic iron cycle.